使用双缓冲 Java Applet 停止小程序闪烁 [英] stop applet flickering with double buffering Java Applet
问题描述
很抱歉一直问关于我的程序的问题，但我想我快到了，我正在自学 Java，所以请耐心等待.我正在创建一个小程序，当狗对象靠近绵羊时，它会以随机方向在屏幕上移动绵羊对象.让绵羊向随机方向移动需要一些工作，在你们这里的帮助下，它现在可以工作(有点)但是我现在要做的是阻止它在我将对象拖过屏幕时闪烁.我读过双缓冲，我可以让它适用于在主类的paint方法中绘制的项目，但不能让它为我的羊和狗对象工作，这些对象在不同的类中定义为单独的对象.任何帮助都感激不尽.这是我的代码:
sorry to keep asking questions about my program but i think i'm nearly there and i'm teaching myself java so please bear with me. I'm creating an applet that moves sheep object across the screen in a random direction when a dog object moves close to the sheep. Getting the sheep to move in a random direction took some work and with the help of you guys on here it now works (sort of) but what I'm trying to do now is stop it from flickering when i drag objects across the screen. I've read about double buffering, I can get it to work for items drawn in the paint method of a main class but cant get it to work for my sheep and dog objects which are defined as separate objects in separate classes. Any help will be much appreciated. Here is my code:
package mandAndDog;
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;
public class SheepDog extends Applet implements ActionListener, MouseListener, MouseMotionListener
{
/**
*
*/
private static final long serialVersionUID = 1L;
/**
*
*/
Dog dog;
Sheep sheep;
int[] directionNumbersLeft = {0, 1, 3};
int[] directionNumbersUp = {0, 1, 2};
int x;
int selection;
int xposR;
int yposR;
int sheepx;
int sheepy;
int sheepBoundsx;
int sheepBoundsy;
int MAX_DISTANCE = 50;
int direction;
int distance;
Boolean sheepisclosetodog;
public void init()
{
addMouseListener(this);
addMouseMotionListener(this);
dog = new Dog(10, 10);
sheepx = 175;
sheepy = 75;
sheep = new Sheep(sheepx, sheepy);
sheepBoundsx = 30;
sheepBoundsy = 30;
direction = (int)(Math.random()*4);
distance = (int) (Math.random() * MAX_DISTANCE) % MAX_DISTANCE;
sheepisclosetodog = false;
Random rand = new Random();
x = rand.nextInt(3);
selection = directionNumbersLeft[x];
}
public void paint(Graphics g)
{
dog.display(g);
sheep.display(g);
g.drawString(Integer.toString(distance), 85, 100);
g.drawString(Integer.toString(direction), 85, 125);
g.drawString(Integer.toString(selection), 85, 140);
}
public void actionPerformed(ActionEvent ev)
{}
public void mousePressed(MouseEvent e)
{}
public void mouseReleased(MouseEvent e)
{}
public void mouseEntered(MouseEvent e)
{}
public void mouseExited(MouseEvent e)
{}
public void mouseMoved(MouseEvent e)
{
}
public void mouseClicked(MouseEvent e)
{}
public void mouseDragged(MouseEvent e)
{
dog.setLocation(xposR, yposR);
sheep.setLocation(sheepx, sheepy);
if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
&& yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 0){
sheepx = sheepx + 50;
direction = (int)(Math.random()*4);
}
if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
&& yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 1){
sheepy = sheepy + 50;
direction = (int)(Math.random()*4);
}
if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
&& yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 2){
sheepx = sheepx - 50;
direction = (int)(Math.random()*4);
}
if (sheepx <= 5){
direction = directionNumbersLeft[x];
}
if (xposR > (sheepx - 20)&& xposR < (sheepx - 20)+(sheepBoundsx - 20) && yposR > (sheepy - 20)
&& yposR < (sheepy - 20)+(sheepBoundsy - 20) && direction == 3){
sheepy = sheepy - 50;
direction = (int)(Math.random()*4);
}
if (sheepy <=5){
direction = directionNumbersUp[x];
}
xposR = e.getX();
yposR = e.getY();
repaint();
}
}
class Dog
{
int xpos;
int ypos;
int circleWidth = 30;
int circleHeight = 30;
public Dog(int x, int y)
{
xpos = x;
ypos = y;
}
public void setLocation(int lx, int ly)
{
xpos = lx;
ypos = ly;
}
public void display(Graphics g)
{
g.setColor(Color.blue);
g.fillOval(xpos, ypos, circleWidth, circleHeight);
}
}
class Sheep
{
int xpos;
int ypos;
int circleWidth = 10;
int circleHeight = 10;
public Sheep(int x, int y)
{
xpos = x;
ypos = y;
}
public void setLocation(int lx, int ly)
{
xpos = lx;
ypos = ly;
}
public void display(Graphics g)
{
g.setColor(Color.green);
g.fillOval(xpos , ypos, circleWidth, circleHeight);
g.drawOval(xpos - 20, ypos - 20, 50, 50);
}
}
推荐答案
首先，我不太明白为什么你的 Sheep 和 Dog 类中有一个 display 方法.与其这样做，我建议您在 SheepDog 类中显示羊和狗.
First of all, I dont exactly understand why you have a display method inside your Sheep and Dog class. Instead of doing that, I suggest you display the sheep and dog inside your SheepDog class.
此外，您应该使用 Graphics2D，而不是使用 Graphics.为了使用这个简单地做
Also instead of using Graphics, you should use Graphics2D. In order to use this simply do
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
}
这是可能的，因为 Graphics2D 是 Graphics 的子类.一旦你这样做了，我会做的是覆盖 update() 方法并执行此操作
This is possible because Graphics2D is a subclass of Graphics. Once you do that, what I would do is override the update() method and do this
public void update(Graphics g) {
if (image == null) {
image = createImage(this.getWidth(), this.getHeight());
graphics = image.getGraphics();
}
graphics.setColor(getBackground());
graphics.fillRect(0, 0, this.getWidth(), this.getHeight());
graphics.setColor(getForeground());
paint(graphics);
g.drawImage(image, 0, 0, this);
}
当你调用repaint()时，它实际上首先调用了update()方法，而后者又调用了paint()方法.在班级的顶端，你应该声明
When you call repaint(), it actually first calls the update() method, which in turn calls the paint() method. Towards the top of the class, you should declare
Image image;
Graphics graphics;
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